[Simh] simh API

[Holger Veit]

Am 14.07.2015 um 19:44 schrieb pigi:
> Il 14/07/2015 19:25, Bill Cunningham ha scritto:
>>      I am not quite sure if I have ask this, or something similar 
>> before. If so please forgive me. Is there a simh tutorial as an API ? 
>> There is simh_doc.doc but it is kind of limited in scope. If someone 
>> were interested in using the API as a simulator for a C128's 650x 
>> processor, how would they begin? If anyone has done anything like this.
>>
>>      I have brought up the CBM computers before. Is there an API 
>> tutorial?
>
> sir, I must point to you that, AFAIK the CBM machines's peculiarities 
> isn't easy to adapt to the general structure of SIMH, even with an 
> graphic API for SIMH (a WIP, as I understand), and, OTOH, there's 
> already a very fine and mature emulator/simulator for the CBM machines:

I don't see specific peculiarities of CBMs which would prevent writing a 
SIMH simulator for them. SIMH was originally tailored to minis that are 
composed of some CPU/RAM/MMU core (albeit distributed over several 
boards) that use some bus system to talk to more or less independent 
and/or intelligent subsystems. This is expressed by the datastructures 
of DEVICEs and UNITs.
  This is different from a microcomputer system where several closely 
interconnected peripheral chips are grouped around a central CPU chip. 
Thus, it is not directly obvious, what can be considered a device or 
unit, besides that some chips like a FD controller or a PIA/VIA (in case 
of a Commodore) require rather low level programming, and turn out quite 
complex.

There are already approaches for simulating micros in SIMH though, the 
Z80 family, the 6800 Flex system, or the 68k-SageII, so I'd see this 
just as quite some work to do, but no actual architectural problem in 
SIMH which would prevent it to implement.

A valid point ist of course that VICE ist already existing, and does a 
good job already for a lot of CBM software, so rewriting this in SIMH 
looks to me like a larger exercise, not really filling a gap.

-- 
Holger


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